1. Field of the Invention
The present invention relates to a commutator assembly for a motor in which conductive wires are electrically connected to a hook formed on one side of a commutator segment of a commutator.
2. Description of the Related Art
FIG. 13 is a front sectional view of a main portion of a conventional motor, FIGS. 14 to 16 are enlarged views of a main portion of a commutator assembly and show respective steps until coils are locked to hooks.
The motor includes a cylindrical yoke, a permanent magnet composed of four ferrites secured in the yoke in a peripheral direction at intervals, a shaft 1 disposed in the yoke through bearings so as to be rotate freely, an armature 2 secured to the shaft 1, and a commutator assembly 3 disposed on one side of the armature 2. Note that the yoke and the permanent magnet are not illustrated.
The armature 2 is composed of an iron core 4 and a winding 5. The iron core 4 has a plurality of slots extending in the axial direction thereof, and the winding 5 is composed of a first coil 6a, a second coil 6b, and a third coil 6c each formed of an enamel-coated copper conductive wire wound around the slots. The winding 5 is constructed by a so-called lap winding method by which a conductive wire is wound, for example, 10 times, then it is displaced by one slot and wound 10 times again.
The commutator assembly 3 is composed of a commutator 8 and four brushes which are placed at equal intervals and caused to come into contact with the surface of the commutator 8 by the elastic force of springs. The commutator 8 is secured to an end of the shaft 1 and composed of commutator segments 7 as many as a plurality of slots disposed on the shaft 1 in the peripheral direction thereof and a base 16 for supporting the commutator segments 7. Locked to the respective hooks 10 of the commutator segments 7 are equalizers 9, which electrically connect commutator segments 7 that should have the same electric potential to each other and come into intimate contact with a side of the commutator 8. The enamel-coated equalizers 9 prevent the occurrence of circulating currents which flow to the brushes due to the difference of voltages induced between the circuits of the winding 5.
In the above motor, the shaft 1 having the iron core 4 secured thereto is inserted into the commutator 8 having the equalizers 9 locked to the hooks 10 and attached to the side thereof. Next, although the winding 5 is formed by winding the coils 6a, 6b, and 6c around the slots of the iron core 4 by the lap winding method, they are locked to the respective hooks 10 of the commutator segments 7 while they are being wound. Thereafter, the respective hooks 10 are electrically connected to the equalizers 9 and the coils 6a, 6b, and 6c, respectively at the same time.
FIG. 14 is a sectional view of a main portion of the commutator assembly 3 before the hook 10 is bent, FIG. 15 is a view when the equalizer 9 and the coils 6a, 6b, and 6c are locked to the hook 10, and FIG. 16 is a view when the hook 10 is bent and then electrically connected to the equalizer 9 and the coils 6a, 6b, and 6c. The electric connection is executed by so-called fusing. That is, the enamel coating of the equalizer 9 and the coils 6a, 6b, and 6c is burnt by Joule's heat by flowing a low voltage and a large current to the hook 10 through an electrode pressed against a surface of the hook 10 so that the equalizer 9 and the coils 6a, 6b, and 6c are caused to be in contact with the commutator segment 7 under pressure, whereby the hook 10 is electrically connected to the equalizer 9 and the coils 6a, 6b, and 6c. 
In the motor arranged by the lap winding method as described above, the armature 2, the equalizers 9 and the commutator 8 which are secured to the shaft 1 are rotated together with the shaft 1 by an electromagnetic action by a current supplied to the winding 5 from the outside through the brushes in contact with the commutator segments 7.
In the commutator assembly 3 arranged as described above, the surfaces of the commutator segments 7 in contact with the brushes and the surfaces of the commutator segments 7 facing the hooks 10 are flat. Thus, when the coils 6a, 6b, and 6c are pressed and deformed, the rate of deformation of the coil 6a at the extreme end of the hook 10 is larger than that of the coil 6c at the root of the hook 10, that is, the rates of deformation of the coils 6a, 6b, and 6c are not uniform, from which the following problems arise:                a) when the equalizer 9 at the root of the hook 10 is appropriately deformed to secure the reliability of electric contact of the commutator segment 7 with the equalizer 9 and to secure the mechanical strength of the equalizer 9, the coil 6a on the extreme end side of the hook 10 is more deformed. Thus, the reliability of mechanical strength of the coil 6a is lowered by the excessive deformation thereof, whereby the coil 6a is liable to be broken. This tendency is more remarkable as the number of coils locked to the hook 10 increases; and        b) when the deformation of the coils 6a, 6b, and 6c is suppressed to an appropriate degree of deformation to secure the reliability of electric contact of the commutator segment 7 with the coils 6a, 6b, and 6c and to secure the reliability of mechanical strength of the coils 6a, 6b, and 6c, the equalizer 9 at the root of the hook 10 is insufficiently deformed, which lowers the reliability of electric contact of the equalizer 9. In particular, this tendency is remarkable when the equalizer 9 is composed of a material having high mechanical strength and difficult to be deformed such as a brass wire, a red brass wire, and the like. Further, this tendency is remarkable when the equalizer 9 has a small wire diameter.        
Furthermore, while the rates of deformation of the coils 6a, 6b, and 6c are controlled by an amount of crush of the hook 10, there is also a problem that it is difficult to control the rates of deformation of them because the amount of crush is dispersed.